ORIGIN OF SEDIMENT-HOSTED HUNTITE DEPOSITS IN THE EGIRDIR-HOYRAN LAKE BASIN OF SOUTHERN TURKEY: ELEMENT CONTENTS AND STABLE ISOTOPE STUDY.

Sediment-hosted huntite deposits are located around Asagitirtar village in the Egirdir-Hoyran Lake Basin, (Yalvac-Isparta, Southern Turkey). The deposits occur at two different localities in the region: (1) Kemersırtı huntite deposit, (2) Koytepe huntite deposit. The huntite occurrences are found in the lacustrine rocks of the Miocene- Pliocene Kizilcik formation, and are interbedded with clayey limestone, dolomitic limestone, marl, and limestone. The mineralogy of the huntite deposits composed of mostly huntite and locally magnesite, dolomite, calcite, illite, quartz, and smectite. The contents of major oxides in the huntites are as follows: MgO varies from 32.70% to 37.95%, SiO2 from 0.99% to 10.60%, and CaO from 7.83% to 15.10%. Ba and Sr are dominant minor elements in the deposits. Ba and Sr contents vary from 65 ppm to 233 ppm and from 325 ppm to 765 ppm, respectively. As contents varies 13-146 ppm, U from 0.5 ppm to 3.9 ppm, Zr from 1.1 ppm to 16.7 ppm, V from 7 ppm to 34 ppm, and Ce from 1.0 ppm to 5.3 ppm. The δ18O and δ13C isotope compositions of huntite samples in the Kemersirti area vary between 30.4‰ to 32.4‰ and 7.8‰ to 8.8‰, respectively. Huntite and magnesite samples in the Koytepe area have 35.5‰ to 29.8‰ for δ18O and 8.3‰ to 1.7‰ for δ13C isotope values, respectively. The presence of nodular huntite and the abundance of gastropod, ostracode and Chura shells in the carbonate units indicate that the huntite occurrences are precipitated at shallow, alkaline (8.5-9.5 pH) and lower temperature (approximately 25°C) lake conditions. The Mg++, Ca++ and Si++ ions for the huntite formation were derived from the surrounding rocks such as ultrabasic rocks, dolomite, dolomitic limestone, and limestone. Also, the isotope ratios indicate that the CO2 source for the huntite formations results to sedimentary basin from meteoric water and carbonate rocks. [ABSTRACT FROM AUTHOR]